I agree with Steve on the registration point. Here, in New Zealand, all trailers, be they caravans, horse boxes, car trailers or just trailers, have to be registered as a vehicle to be used on the road. They have an annual registration fee, and therefore disc, have their own number plate and what is more are required to undergo a "warrant of fitness" (MOT) annually to ensure road worthiness, a double bonus.
Kiwi Pete.